Sounds like you need to start from scrath. Try getting a working psu with at least 450watts+ to plug your pc. Just plug your hdd, mobo, and dvd/cd drive , dont connect any fans for your case. your psu may have limited its power or its not working at all. This may sound crazy, you said your psu is working but i have seen psu working but with dead or half dead connections. Also try geting a good or better fan for your processor , your processor may be overheating. you should keep it between 32-39 for optimal performance, 40-60 for regular. 61+ dont ask.